"It was done very swiftly, precisely, and she was extracted from there in a matter of a few seconds," he said of the girl.

"It was certainly a big risk and we`re going to praise the courage of the officers who broke into the confined space, that barricaded space, believing that that person had a bomb."

The incident was the second in as many months in which Sydney has been hit by an explosives scare, with teenager Madeleine Pulver making worldwide headlines in August after finding herself at the centre of a collar bomb hoax.

A man was arrested in the United States over the incident but charges are yet to be laid.